A digital light processing (DLP) projection device includes an illumination system, a digital micro-mirror device (DMD) and a projection lens. The illumination system is used to provide an illumination beam, the digital micro-mirror device is used to convert the illumination beam into an image beam, and the projection lens is used to project the image beam onto a screen to form an image screen on the screen. In general, an early illumination system uses an ultra-high pressure mercury lamp as a light source, and the ultra-high pressure mercury lamp can provide white light as an illumination beam. With the development of illumination technology, other light sources such as light-emitting diode light source and laser light source having an energy-saving advantage are gradually being used.
FIG. 1 is a schematic view of a conventional illumination system using a laser light source. As shown in FIG. 1, in the conventional illumination system 100, a blue beam 112 provided by a laser light source module 110 sequentially passes through a collimating element 122, penetrates a dichroic mirror 130, passes through lenses 123, 124, and is irradiated to a rotatable phosphor wheel 140. The phosphor wheel 140 may be divided into a green phosphor region, a yellow phosphor region, an opening region, etc., wherein a back surface 141 of the green phosphor region and the yellow phosphor region of the phosphor wheel 140 are correspondingly disposed with a reflection element (not shown). The blue beam 112 is sequentially irradiated to the green phosphor region, the yellow phosphor region and the opening region. A green beam 113 and a yellow beam 114 are excited when the blue beam 112 is irradiated to the green phosphor region and the yellow phosphor region respectively, and the reflection element reflects the green beam 113 and the yellow beam 114 back to the dichroic mirror 130. Then, the green beam 113 and the yellow beam 114 are reflected by the dichroic mirror 130, pass through a lens 125 and are irradiated to a rotatable phosphor wheel 150. In addition, a portion of the blue beam 112 sequentially penetrates the opening region, passes through lens 126, 127, reflection elements 161, 162, a lens 128, a reflection element 163, a lens 129, the dichroic mirror 130, the lens 125 and is irradiated to the color wheel 150.
The color wheel 150 has a red light filter region and a transparent region corresponding to the yellow phosphor region, a green light filter region corresponding to the green phosphor region and a diffusion region corresponding to the opening region. By the control of the color wheel 150 and the phosphor wheel 140 to rotate with each other, the green beam 113 is irradiated to the green light filter region, the yellow beam 114 is irradiated to the red light filter region and the transparent region, and the blue beam 112 is irradiated to the diffusion region. Thus, the beam entering a light integration rod 170 after passing through the color wheel 150 includes a blue beam, a green beam and a red beam for forming a color image and a yellow beam for increasing the luminance.
Since having a complicated structure and requiring many optical elements, the conventional illumination system 100 has some disadvantages such as high cost, large volume and poor optical efficiency.
The information disclosed in this “BACKGROUND OF THE INVENTION” section is only for enhancement understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Furthermore, the information disclosed in this “BACKGROUND OF THE INVENTION” section does not mean that one or more problems to be solved by one or more embodiments of the invention were acknowledged by a person of ordinary skill in the art.